The order of Ustilaginales comprises pathogenic fungi of many important crop plants, including corn smut caused by Ustilago maydis. Besides the plant pathogenic species, anamorphic yeasts have been identified within the smut fungi. One example is Moesziomyces sp., which has been found on Arabidopsis thaliana (Agler et al., 2016 ) and has no pathogenic sexual morph (Kruse et al., 2017). Moesziomyces sp. was found to be a key regulator of the Arabidopsis leaf microbial community in the presence of hub microbes. Moreover, Moesziomyces sp. significantly antagonizes the infection by the oomycete pathogen Albugo laibachii, a major hub connecting host genotype with microbe-microbe interactions and environmental factors. In my PhD project I want to functionally characterize antagonistic genes in Moesziomyces sp. to establish it as a biological control agent. I also want to analyze the significance of life style change of Moesziomyces sp. from haploid to filamentous form in the microbial community of A. thaliana leaf surface.